The electronic configuration of ${\mathrm{Mn}}^{x+}$ ion is $\left[\mathrm{Ar}\right]$ $3{\mathrm{d}}^4.$ The value of ${}^{\text{'}}x^{\text{'}}$ is _________.

Which of the following compound is expected to show similar magnetic behaviour?

(Atomic number of$\mathrm{Fe}$ is $26, \mathrm{Cu}$ is $29, \mathrm{V}$ is $23, \mathrm{Mn}$ is $25$)

 $\mathrm{A}$ and $\mathrm{B}$ in the following reaction, respectively, are:

${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7+\mathrm{HCl} \to \mathrm{KCl}+\mathrm{A}+\mathrm{B}+{\mathrm{H}}_2\mathrm{O}$

Which of the following reactions are disproportionation reactions?

$\left(\mathrm{i}\right)$ ${\mathrm{Cu}}^{+}⟶{\mathrm{Cu}}^{2+}+\mathrm{Cu}$
$\left(\mathrm{ii}\right)$ $3{\mathrm{MnO}}_4^{-}+4{\mathrm{H}}^{+}⟶2{\mathrm{MnO}}_4^{-}+{\mathrm{MnO}}_2+2{\mathrm{H}}_2\mathrm{O}$
$\left(\mathrm{iii}\right)$ $2{\mathrm{KMnO}}_4⟶{\mathrm{K}}_2{\mathrm{MnO}}_4+{\mathrm{MnO}}_2+{\mathrm{O}}_2$
$\left(\mathrm{iv}\right)$ $2{\mathrm{MnO}}_4^{-}+3{\mathrm{Mn}}^{2+}+2{\mathrm{H}}_2\mathrm{O}⟶5{\mathrm{MnO}}_2+4{\mathrm{H}}^{+}$